Grinder gas, that is the gas which is released from roasted whole coffee beans when their internal cell structure is disrupted, such as during grinding of the beans and which also continues to be evolved from the disrupted and/or fractured beans for a short period thereafter, has long been recognized in the art as a highly desirable natural coffee aroma. The collection and stabilization of this aroma has, however, proven to be a difficult undertaking, especially when it is desired for use in a commercial-sized soluble coffee system.
The use of grinder gas as a means to enhance the jar aroma of a soluble coffee powder is disclosed in U.S. Pat. No. 3,021,218 to Clinton et al. which aromatizes the jar headspace and U.S. Pat. No. 2,306,061 to Johnston which condenses grinder gas aromatics onto chilled soluble coffee powder. The use of grinder gas condensates which are added to a liquid extract and dried in order to produce an improved cup aroma when the powder is dissolved in hot water is disclosed in U.S. Pat. No. 3,244,533 to Clinton et al. which homogenizes coffee oil in extract and then adds condensed grinder gas aromatics. Condensed grinder gas frost can be mixed with a liquid glyceride which mixture is then processed to remove excess water, such as by centrifugation, prior to being combined with soluble coffee solids (e.g., soluble powder).
The addition of the condensed aromatics to a glyceride carrier is a known method for stabilizing the aromatics. Such glycerides as coffee oil, bland-tasing vegetables oils and triacetin have proven especially useful for this purpose; however, other oils and low melting point fats may also be used. U.S. Pat. No. 4,119,736 to Howland et al. discloses removal of a water phase from a pressure vessel containing condensed grinder gas at a pressure of in excess of 506.2 psia and a temperature of greater than 32.degree. F., contacting the demoisturized grinder gas with a glyceride, and slowly venting the pressure vessel. Mahlmann in U.S. Pat. No. 3,979,528 discloses a method for aromatizing a glyceride by contacting it with a grinder gas frost in a pressure vessel at various conditions. Among the conditions disclosed by Mahlmann is a rapid pressure release of the pressure vessel to atmospheric pressure at a temperature below room temperature.
It has, however, been desired to maximize the amount of aromatics that are fixed in the glyceride carrier so as to minimize aroma loss and reduce the amount of glyceride which would be incorporated with a soluble coffee product so as to obtain a desired level of aromatization. Moreover, it is desirable to increase the quantity of aromatics generally but especially the aromatics having or imparting a "lighter", "high impact", "groundsy", "buttery", "less sulfury" character to the soluble coffee.